1. Field of the Invention
The present invention relates to systems and methods for cost-efficient routing of digitally encoded messages using, as appropriate, private networks and public-switched telephone networks.
2. Background of the Invention
FIG. 1 is a schematic diagram of a prior art point-to-point delivery system for digitally encoded message (DEM) data. Message communicating device (MCD) 1 uses public-switched telephone network (PSTN) 3, which provides a direct path from MCD 1 to PSTN 3 through connection 10. PSTN 3 then establishes connection 30 to MCD 5, creating an end-to-end connection between MCD 1 and MCD 5, such that MCD 1 can transmit the DEM data to MCD 5. In the reverse direction, MCD 5 can establish connection 70 to PSTN 3, which then establishes connection 90 to MCD 1, and again the DEM data is transmitted to MCD 1.
FIG. 2 is a schematic diagram of a second prior art message delivery system. In this system, MCD 1 uses a Store-and-forward Message Handler (SFMH) 4, which can provide send-side service (store-and-forward functionality), receive-side service (mailbox functionality), or both, to MCD 1. When MCD 1 sends a DEM to MCD 5 , MCD 1 establishes connection 10 to PSTN 3, as in the prior art system of FIG. 1. However, PSTN 3 then establishes a connection 41 to SFMH 4 (instead of directly to MCD 5). The DEM data is then transferred from MCD 1 to SFMH 4, and stored electronically by SFMH 4. Connection 41 is no longer needed. After connection is discontinued, SFMH 4 is charged with forwarding the same DEM data to MCD 5, through connections 51 and 31.
In the reverse direction, SFMH 4 can receive DEM data addressed to MCD 1 from MCD 5. The first transmission is made by MCD 5 to SFMH 4 using connections 70 and 42. SFMH 4 then stores the DEM data, and either:
(1) awaits pickup from MCD 1--in which case MCD 1 initiates pickup through connection 13 to PSTN 3, which creates connection 43 to SFMH 4; or PA1 (2) pro-actively calls MCD 1 through connections 51 and 11, and the DEM data is transmitted from SFMH 4 to MCD 1.
The prior art system of FIG. 2 can lower costs by deferring delivery of low-priority long-distance messages until rates are lower, and can also make repeated attempt to deliver the DEM. However, the system can provide cost efficient store and deliver or mailbox services to only one side, e.g., to MCD 1, because the other side would have to pay for long-distance rates to use the SFMH.
FIG. 3 is a schematic diagram of another prior-art system, in which two SFMHs are used to minimize telephone costs. PSTN 3 in FIGS. 1 and 2 was defined as a single entity, because all telephone calls are made to and from the PSTN located nearest to MCD 1 (in FIG. 1) or SFMH 4 (in FIG. 2). FIG. 3 shows a PSTN 3a which has the same relationship to SFMH 8a as PSTN 3 has to SFMH 4 in the FIG. 2. However, this system also includes PSTN 3b, which is the PSTN located nearest to SFMH 8b.
In this system, MCD 1 establishes connections 10 and 41 through PSTN 3a, and the message is transferred to and stored on SFMH 8a. PSTN 3a in this case is local to MCD 1, but not to MCD 5 (otherwise the message could just as well have been sent directly to MCD 5 from PSTN 3a). This system uses connection 49 between SFMH 8a and SFMH 8b, instead of long-distance connection 31 of FIG. 2. Connection 49 is a long-distance data connection that can be conducted at speeds far greater than the speeds that can be provided by an ordinary long-distance PSTN connection. In this case, SFMHs 8a and 8b are nodes in the transmission system, and connection 49 is a high-speed inter-nodal connection. Finally, connection 32 is local to MCD 5, such that its cost will be substantially lower than the costs of the long distance connections used in the system shown in FIGS. 1 and 2.
FIG. 4 represents a typical electronic mail (E-mail) system. Inter-nodal connection 49 is referred to as a gateway between the SFMHs. The problem with such E-mail systems is that such gateway networks have been developed for only one specific DEM data type, in which free-form text is represented by the ASCII character set.
FIG. 5 is a schematic diagram of a system disclosed in U.S. Pat. No. 5,369,686, which is hereby incorporated by reference. In the system of FIG. 5, an Enhanced Service Exchange Device ESX 2 is placed between MCD 1 and PSTN 3. The user of MCD 1 simply inputs only the address, e.g., the telephone number, of MCD 5. ESX 2 receives the address and the DEM over connection 11, and then establishes telephone connection 10 and 41 to SFMH 4, via PSTN 3.